Multiaxis controlled motion knee orthosis

ABSTRACT

The present invention relates to an appliance for controlling an unstable knee joint in the sagittal, coronal and transverse planes, comprising femoral and tibial cuffs joined by links which are interconnected to provide a novel mechanical joint wherein camming slots are formed in one of the links with cams disposed on the other link, the slots comprising straight segments and arcuate segments so as to provide approximately 8 millimeters of sliding movement between the femur and tibia, followed by relative rotation about the center of radius of the femoral condyle as the leg is flexed. The tibial cuff is conformed about the boney prominence or shin of the tibia to inhibit rotation of the leg beneath the knee within the brace itself.

This application is a division of application Ser. No. 792,770 filedOct. 30, 1985 now U.S. Pat. No. 4,723,539 which is acontinuation-in-part of my co-pending application, Ser. No. 06/639,866filed on Aug. 13, 1984 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to orthopaedic devices for thestabilization and control of a human knee joint along several axes andhas as its primary purpose the stabilization of the knee joint which hasbeen injured. Stabilization and control is achieved in such a manner asto permit the user relative freedom in the normal use of the boneswhile, at the same time, permitting control over the joint so as tooptimize healing.

The human knee is acknowledged as one of the weakest joints in the body.It is the articulating joint between the thigh and calf muscle groupswhich support the body's weight while walking or running, and it is heldtogether primarily by two small but powerful ligaments, the anterior andposterior cruciate ligaments. Knee instability arising out of cartilagedamage, ligament strain and other such causes is relatively commonplacesince the knee joint is subjected to significant loads during the courseof almost any kind of physical activity requiring the use of the legs.Devices for adding support and strength to the knee joint have beenknown at least since the very early Sears and Roebuck catalogs, whichprovided elasticized support members intended to circumscribe the jointto apply a squeezing pressure which results in a "feeling" of additionalsupport even though that support may be physiologically minimal.

While the public has been sports-minded for years, it was not until thelate 1960's, with a great increase in the volume of televisedprofessional sports, and very highly paid athletes, and, in particular,contact sports such as football, basketball and soccer, that sportsmedicine, as a specialized field, evolved. Until that time, knee bracestypically consisted of two sets of links connected by a pivot pin whichwere disposed on either side of the knee and sewn into an elasticizedsleeve which was slipped over the knee joint like an elastic sock sothat the pivot pins were disposed on either side of the knee. Suchdevices afforded virtually no protection to an athlete engaged in acontact sport, or in a sport where there is a large amount of stressplaced on the knee joint due to running, jumping, pivoting and the like.

2. Survey of the Prior Art

Perhaps one of the first and most highly publicized breakthroughs, or atleast advances in knee orthoses, occurred when the Lennox Hill brace wasdeveloped to protect the knees of Joe Namath, then one of the highestpaid athletes in any sport. Several deficiencies in the Lennox Hilldesign have been recognized, however, and sports medicine people havespawned a plethora of other braces in attempts to improve kneestabilization. The designs include single and double pivot designs,although the double pivot design available typically includes a centerlink with pivot points at each end, and with the center link beingaxially aligned with the femur and tibia. Among such braces are includedthe model 4521 offered by Orthopedic Systems, Inc. of Hayward, Calif.,and the polyaction knee orthosis offered by Scott Orthopedic Labs inDenver, Colo. Still another, called c.t.i. brace, is offered byInnovation Sports of Irvine, Calif.

The patent art also offers several exemplars of efforts to stabilizeinjured knee joints, and among them are the following patents:

Foster, U.S. Pat. No. 4,353,361; Gardner, U.S. Pat. No. 3,799,158;Deibert, U.S. Pat. No. 4,271,831; Horne, U.S. Pat. No. 3,779,654;Taylor, U.S. Pat. No. 3,902,482; Gromes, U.S. Pat. No. 1,336,695;Buring, et al., U.S. Pat. No. 4,409,689; Almedia, U.S. Pat. No.4,139,002; and Meierhofer, U.S. Pat. No. 2,379,538.

The bulk of the prior art offerings comprise a variety of braces rangingfrom very simple to quite complex mechanical joints, all of which have aunity of intent, i.e., stabilization of an injured knee. Some of thebraces are intended to protect and stabilize particular injuries andothers are more general in their application. As will become apparentfrom the following detailed description of a preferred embodiment of thepresent invention, however, none of these prior efforts accomplished thehigh degree of stabilization with relative simplicity offered by thepresent invention.

DESCRIPTION OF THE DRAWINGS

With the foregoing as historical perspective, a preferred embodiment ofthe present invention will now be described in detail, which descriptionshould be read in conjunction with the accompanying drawings, wherein

FIG. 1 is a lateral side elevation of the orthosis of the presentinvention shown as mounted to the right leg of the user;

FIG. 2 is a front elevation of the same leg showing the orthosis in adifferent aspect;

FIG. 3 is a perspective of the orthosis showing the overallconstruction, and the arrangement for mounting the same, in itsoperative position, on the user's leg;

FIG. 4 is a sectional view of the orthosis, mounted on the leg, takenalong section 4--4 of FIG. 2, and is intended to show the relativeposition of the orthosis with respect to the tibia and the calf area ofthe leg, to illustrate one of the unique features of the invention;

FIG. 5 is a side elevation of a typical joint of the present invention,indicating the relative position of the components at various stages offlexion of the knee;

FIG. 6 is a side elevation, in partial section, showing the knee jointof FIG. 5;

FIG. 7 is an exploded perspective view of a typical joint of the presentinvention, showing the relative interfitting arrangement of componentsthereof.

FIG. 8 is a lateral side elevation of the orthosis of the presentinvention shown as in FIG. 1, mounted to the right leg of the user, andillustrating certain alternative embodiments, particularly of thefemoral cuff and joint mechanism;

FIG. 8a is a front elevation of a portion of the femoral cuff of FIG. 8illustrating the features thereof, from a slightly differentperspective;

FIG. 9 is a side elevation of an alternative form of the joint mechanismof FIG. 5;

FIG. 10 is an exploded perspective view of the joint mechanismillustrated in FIG. 9;

FIGS. 11 and 12 are side elevations of the joint mechanism illustratingmodifications thereof to permit limitation of extension and flexion ofthe knee joint;

FIG. 13 is a side elevation of a pair of links joined at theirrespective terminus by a joint mechanism to form an articulating strutconstructed in accordance with the present invention for use withvarious orthopaedic appliances;

FIG. 14 is a side elevation of the joint of the strut mechanism of FIG.13; and

FIG. 15 is an exploded perspective view of the camming link of the strutassembly shown in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the drawings, and more particularly to FIGS. 1 and2, a multiaxis controlled motion knee orthosis, or brace, 15 is depictedin its proper mounted position on the right leg of a wearer. So that thefit of the orthosis may be clearly understood, the drawing also depictsthe relative positions of the femur F and the tibia T as well as thepatella P, forming a . . . typical knee joint of an adult male,indicating the alignment of each with respect to the brace 15, with thewearer standing erect and the right leg in the longitudinally extendedposition. The brace 15, as may be seen best in FIG. 3, includes meansfor securing the brace to the leg of the wearer, comprising a pair ofleg grasping devices in the form of an upper thigh, or femoral, cuff 17having a major closure means 19 and a minor closure means 20, both ofwhich are constructed so as to secure and snugly fit the thigh withinthe cuff 17.

The major closure means encircles the entire upper thigh and is,preferrably, of an elastic material, e.g. Latex, so as to provide somegive as the muscles are flexed, and may be of a Latex material, or suchother suitable elastic fabric, as desired. The femoral cuff includes apair of opposed spaced wings 21, adapted to engage the lateral andmedial sides of the thigh. The major closure is attached to the medialwing, such as by rivets 22, and a Velcro closure is provided as at 23.The minor closure 20, attaches to the lateral wing at pivot pin 24 and,as illustrated, employs a "D" ring through which the closure is fed anddoubled back on itself to provide the desired firmness of fit. Onceagain, a Velcro closure, or some other closure, is employed.

A calf, or tibial, cuff 25 is disposed beneath the knee joint andpartially encircles the calf area, as best seen in FIGS. 1 and 2. Inorder to ensure snug fit of the tibial cuff 25, there are providedtransverse closure members 27, of which three are shown inlongitudinally spaced relation. In order to assure a more precise fit,the femoral and tibial cuffs are formed to specially fit the exact legupon which the brace is to be worn. This is accomplished by forming acast about the leg of the intended wearer. The cast is then cut andthereupon serves as a mold to form a model of the leg. Each cuff is thenprecisely fabricated of a laminate material right on the cast in theproper position. In order to provide optimum strength, both graphite andKelvar filaments are used in a liquid resin, which is then formed abouta casting to create the cuffs. Thereafter, the cuffs are lined with somesuitably resilient, shock absorbent material such as, for example,sorbathane, and are ready to wear.

The femoral cuff 17, as previously described, is formed with a pair ofwings positioned relative to one another by a bridge section 26 spanningthe lower part of the thigh above the knee. This construction allowssome freedom to allow the larger, upper thigh muscles to expand andcontract with loss of control. The area engaged by the tibial cuffincludes the greater portion of the calf muscle at the rear of the leg.For that reason, the tibial cuff is more "C" shaped, encircling themajority of the anterior portion of the lower leg, as seen in FIG. 4.The cuff is open at the rear of the leg to permit the cuff to be slippedon, and, further, to permit flexing of the calf muscle when the cuff isin place.

The closure members 27 are of a similar construction to the minorclosure member 20 secured to the femoral cuff. Thus, each memberincludes an elastic strap 28 riveted, or otherwise secured, at somepoint on the medial side of the cuff. A "D" ring is affixed in thelateral plane of the strap by means of a hanger 29 which is shown asattached to the lateral side of the cuff by a fastener 30. The fastener,which may be of any suitable construction, permits limited, essentiallylongitudinal positioned adjustment by rotation of the hanger 29 along apath A--A so as to permit snug fit over the severe contours of the calfas it flexes during movement. As before, the strap may pass through the"D" ring and close by means of Velcro, or some other suitable closuremeans.

While the formation and construction of the femoral and tibial cuffs isan important aspect of the invention as a whole, a major feature of theinvention rests in the construction of the unique mechanical joint 32,which joins the cuffs to define the brace 15 into an orthosis capable ofstabilizing the wearer's knee joint in each of the transverse, coronaland sagittal planes. The detailed construction of the joint 32 of thepresent invention will now be described with respect to such a jointposition at the lateral side of the right knee. It will be appreciatedthat the medial joint is the mirror image of the lateral joint, and thatboth will operate in unison as the leg is flexed.

With reference first, primarily, to FIG. 3, the femoral cuff 17 isprovided with depending, spaced apart, parallel supporting links 34 and35 respectively. As seen in FIG. 3, link 34 is the lateral link and link35 is the medial link. The links 34 and 35 are readily laminated intothe tibial cuff, in a known manner, although it will be appreciated thatthey may be sewn in, or otherwise fastened, without departure from theinvention. The free end of each link 34 and 35, terminates in a bulged,or widened, end. As previously stated, the links are essentiallyparallel and are disposed on the medial and lateral sides of the thigh,respectively, and depending therefrom to and through a transverse planeR--R as shown in FIG. 1. The plane R--R is transverse to thelongitudinal plane of the tibia F and passes through a center point 40,which represents the center of radius of rotation of the femoral condylerelative to the tibia.

In a like manner, the tibial cuff 25 is provided with upwardlyextending, spaced parallel links 44 and 45, respectively, link 44 beingon the lateral side, and link 45 being on the medial side of the cuff,as shown. As in the case of the femoral links 34 and 35, the tibiallinks 44 and 45 extend upwardly, passing through the transverse planeR--R, and each terminates in a widened, or bulged, portion. As in thecase of the femoral links, the tibial links may be molded into, sewn, orotherwise attached, to the tibial cuff in some convenient well-knownmanner. Once again, referring to FIG. 3, it will be seen that thelateral femoral and tibial links 34 and 44 are essentially aligned inadjacent planes such that the terminus of each of the links overlaps andis disposed immediately adjacent to one another in a transverse plane,as is the case with the medial links. In each case, the femoral linksare disposed slightly inwardly of the tibial links, once again, as bestseen in FIG. 6.

Overlapping bulged termini portions of the respectively lateral andmedial links intersect and lie within the plane R--R to provide thenucleus of the highly unique joint mechanism indicated generally at 32and illustrated in detail in FIGS. 5, 6 and 7, respectively. In order toprovide optimum stability for an injured knee, and particularly a kneein which the injury involves either the anterior or posterior cruciateligament, it is necessary to emulate, insofar as reasonably possible,natural, relative movement of the femur and tibia. Most prior artdevices appear to have taken for granted that such movement consists ofa relative rotation about a single center of rotation, typically in thecenter of the knee, which is the philosophy resulting in the familiarsingle pivot brace. Since that is not the natural relative movement ofthe knee joint, such single pivot braces inherently cause undue stressduring flexion of the knee joint, rather than stabilizing, which is theultimate goal of the present brace. In fact, it has been found thatcommencing from the leg extended position, the initial movement of thetibia relative to the femur through the first 25° of flexion is anapproximately 8 millimeter front to rear slide, followed by rotation asthe knee continues to flex through a 125° angle, or for whatever anglemay be traversed, as limited by the injury or natural limitations. Ithas been determined that if the knee is permitted to move in a naturalfashion, stress on the cruciate ligaments and the quadriceps muscles,which play a major role in the function of the knee, is so minimal thatan injury to the knee is actually permitted to heal more effectivelywhen the user wears the brace of the present invention.

With the foregoing biomechanics in mind, the joint mechanism of thepresent invention is constructed to permit the knee joint to beconstrained to move with the natural glide and rotation of a normalknee, to, thereby, protect the injury and minimize stress by theprovision of spaced camming devices, which as illustrated, take the formof longitudinally spaced camming slots 55 and 57, respectively. For thepurposes of identification, the camming slot 55 will be referred to asthe femoral camming slot and camming slot 57 may be referred to as thetibial camming slot. Each slot is formed in a straight line segment 60and 62, respectively, which adjoins arcuate segments 64 and 66,respectively. It will be noted that the straight line segments 60 and 62terminate at the end remote from the juncture with the arcuate segments64 and 66 on the plane R--R. It will also be noted that the arcuatesegments are generated about the same radial center which is alignedwith the center point 40.

The camming slots are adapted to receive and operate in conjunction withthe camming follower means, which, as illustrated, comprise screws 73and 75. As illustrated in FIG. 7, a two-part post and screw assemblymanufactured by Chicago Screw is shown, although other forms of cammingdevices could be employed. The camming screws 73 and 75 pass throughholes 77 and 78 formed in the terminus 80 of the femoral link (freeend). The holes 77 and 78 lie in plane R--R. Bushings 82 are provided,having an inside diameter sufficient to fit over the circumferentialsurfaces of the posts 73 and 75 in bearing relation with respectthereto, and an outside diameter sufficient to snugly fit in bearingrelation within the slots 55 and 57, respectively. A cap, or coverplate, 85 having holes 87 and 88, respectively, permit the receipt ofposts 73 and 75, which are then secured by screws 90 to form the joint.The cover plate not only holds the screws, but further serves as areaction member, sandwiching the bulged terminus of the tibial linkbetween the plate 85 and the bulged terminus 80 of the femoral link, asbest seen in FIG. 6, such that relative movement of the femoral linkrelative to the tibial link is strictly controlled by movement of theposts 73 and 75 in the slots 55 and 57, respectively. In FIGS. 5, 6 and7, there is shown, by way of example, a lateral joint for the right leg.The medial joint is the mirror image of the lateral joint, so that therelative movement of the lateral and medial links are coordinated andthe same.

In order to achieve optimum relative natural movement of the knee joint,which, of course, is a principal feature of the present invention, theinteraction of the femoral and tibial surfaces must be taken intoaccount. To this end, while both straight segments 60 and 62 begin withpins 73 and 75, resting in plane R--R, when the leg is extended andessentially straight (see FIG. 5), as flexion begins, there is anapproximate 8 millimeter lateral movement between the tibial and femoralsurfaces, which is permited as the pins slide along the straightsegments 60 and 62. In a very tall person, the slide may be slightlylonger, and in a small child, it may be shorter, and the precise lengthof the slot may be adjusted to meet specific conditions. A range of 6 to9 millimeters meets most needs. The slide of the femur and tibia,however, does not take place in plane R--R, but, rather, a slightrelative tilt is experienced as the leg is flexed through the first 25°of flexion. To accommodate this movement, the straight line segment 60forms a 50° angle with the plane R--R, whereas, the straight segment 62forms an angle of 56° 30'. Thus, as the leg is flexed through the first25° of flexion, camming posts 73 and 75 respectively, move in a straightline along the straight segments 60 and 62, each at the previouslydisclosed angle. There is a small tolerance permitted to meet specificneeds, but most needs are met within ±2° of the angles herein specified.At 25°, they intersect the arcuate sections 64 and 66, respectively, atintersections 94 and 96. Beyond 25° of flexion, the natural movement ofthe knee through further flexion is a relative rotation of the tibiarelative to the center point 70 on the femoral condyle. In order thatthis movement may be emulated with the greatest possible accuracy,arcuate sections 64 and 66 have been formed around center point 70 andit has been found that a radius of 0.43 inches, or 11 millimeters,provides the desired resultant rotational movement in a typical knee.Approximately 96° 30' is required to provide full knee flexion. It willbe appreciated, however, that if a lesser knee flexion is requiredbecause of the particular instability found in the user's knee, the arcmay traverse a greater or lesser angle without departure from theinvention. Indeed, stops may be used to limit flexion simply byinserting a blocking device of known construction and, therefore, notshown, at the appropriate point within the slot 55 and 57 to therebylimit the amount of flexion that the user can experience using thebrace.

While in a normal knee there is a slight outward rotation of the tibiarelative to the femur upon flexion, such rotation may be pronounced inthe case of certain knee injuries resulting in instability. The presentinvention, in still another of its inventive aspects, limits andconstrains such rotation upon flexion of the knee, thereby enhancing thestability thereof. This is accomplished, as best seen in FIG. 4, byforming, or molding, the tibial cuff over the anterior boney prominence100 of the tibia, sometimes referred to as the shin. As seen in FIG. 4,the cuff has been molded, or formed, about that prominence, such thatany tendency of the tibia to rotate about its longitudinal axis uponflexion is resisted by the cuff. The structure of the cuffs and links isof such integrity that not only is rotation controlled within the cuff,but when the leg is flexed, the wings 21 of the femoral cuff, work withthe tibial cuff by acting against the wearer's thigh through the linksto resist any rotation of the brace, thereby totally inhibitingundesirable rotation. In order to avoid irritation by rubbing of thetibia against this tightly molded section of the cuff, a spongeymaterial, such as sorbathane, may be provided in this area about theinterior of the cuff, at or about the location 99, or about the entirearea which contacts the skin of the wearer if it is so desired. Strongclosure members 27, 28 and 29, of course, permit the tibial cuff to beheld in position firmly against the shin, while at the same time,minimizing the discomfort which might otherwise be experienced by thewearer.

With particular reference now to FIGS. 8 through 10, several novelalternative structures are illustrated in detail. In stabilizing manyinjuries, it is essential to minimize torsional rotation of the femurand upper thigh relative to the lower legs. To this end, and withreference to FIG. 8, an orthosis 115 is illustrated in which a femoralcuff 117 is provided having a novel construction particularly adapted toaccomplish the minimization of tortional or twisting movement of thefemur and upper thigh relative to the lower leg of the wearer.

The beneficial features of this modified femoral cuff 117 areaccomplished by the provision of a continuous band 118 which is moldedabout the thigh, embracing the same for approximately 120° of itscircumference. The termini of 119 of the band 118 respectively define arearwardly facing opening through which the users leg may pass to bepositioned within the cuff 117. A pair of spaced minor closure means 120are provided of a construction very similar to that described inconnection with FIG. 3. The overall design, however, may be streamlinedby molding the closure hanger 129 into the cuff.

As best seen in FIG. 8a, the femoral cuff is further formed with alaterally extending opening 122 defined by upper and lower ribs orbridges 123 and 124 respectively formed integrally with opposed,integrally formed side members or wings similar to those depicted inFIG. 3.

The femoral cuff of FIG. 8, like that of FIG. 3, is an integral unitformed of fiberglass or other moldable material and is constructed toencircle a major portion of the thigh in order to firmly but comfortablyhold the upper leg against torsional rotation with respect to the lowerleg. The void 122 which has the appearance of an elongated ellipsoid,preferably formed by the removal of material from the cast cuff, andresults in a significant lightening of the cuff while maintaining itsstrength. Foam rubber or other material of like property is preferablyattached, as at 27 in order to minimize abrasion between the brace andthe wearer's skin and to further add to the comfort of the wearer.

Still another feature of the modified femoral cuff as shown in FIGS. 8and 8a is seen where the lower bridge 124 is formed, along its loweredge, with a longitudinal narrowing as at 130 which further adds to thecomfort of the wearer by minimizing pressure on the quadriceps musclesand the upper part of the patella when the lower leg is in extension.

Referring now to FIGS. 9 and 10 respectively, yet another embodiment ofone aspect of the invention is illustrated in some detail. Depicted inthose figures is an alternative embodiment of the mechanical jointitself. As in FIG. 7, a mechanical joint 132 is illustrated in FIG. 10as comprising a link 134 depending from the femoral cuff for limitedrotational engagement with an upwardly extending tibial link 144. Asdescribed with respect to FIG. 7 arcuate segments 164 and 166 are formedin the bulging terminal end of the link 144 and posts 173 and 175 aremounted in, and pass through the link 144 and through the arcuatesegments 164 and 166 respectively where they are held in place by acover plate 185.

The arcuate segments 164 and 166 will be seen to govern the relativemovement of the links 134 and 144 respectively. It will also be evidentthat there is significant surface area contact between the linksthemselves as well as between the link 144 and the cover plate 185. As aconsequence of the relatively large surface area of contact, it has beenfound that there is a tendency, in some instances, for the joint tobind, or otherwise stated, to respond to the friction between therelative elements by a reduction in the smoothness and evenness withwhich the joint is articulated. In order to alleviate this possibleoccurrence without effecting the operation of the joint itself, the capor cover plate 185, in accordance with the invention, is formed with anopening 188 disposed about the center point 170 of the joint. At thecenter point, a post 190 is attached to and extends laterally outwardlyfrom the link 144 where it projects into the opening 188 when the jointis fully assembled. The opening 188 effects a small but significantreduction in frictional drag thereby virtually eliminating the lack ofsmoothness in articulation of the joint which might otherwise resultfrom a binding effect. The post 190 projecting into the opening 188 actsas a further guide to retain the relative positions of the link 144 andthe cover plate 185 in order to assure that the articulation of thejoint is fully controlled by the posts 173 and 175 moving within thearcuate segments 164 and 166 respectively.

In certain cases, an orthopaedic injury or deformity calls for arestriction in the flexion and extension of the articulating knee jointto assure that the user cannot injure him or herself by either extendingor flexing beyond a desirable limit. Another aspect of the invention isto provide, in such cases, means for controlling flexion and/orextension of the knee joint of the wearer. This may be accomplished byanother novel modification of a mechanical joint 232 as best illustratedin FIGS. 11 and 12 respectively. As seen in those figures, the terminalend of either the tibial or femoral link may be formed with an enlargedand extended end portion 244, which may encompass several degrees ofcircumference. The invention contemplated the formation of a slot 246 inthe extension 244, and the provision of a laterally extending post 248on the contiguous link. The post 248 laterally extends into the slotopening 246, the slot having a curvature to permit smooth articulationof the mechanical joint throughout the full length of the slot. Thedesirable result is clearly that the amount of flexion and/or extensionwhich the articulating joint may experience may be limited. In FIG. 11,for example, a traverse of the entire slot distance would limit movementto 45° whereas in FIG. 12 the limitation would be 90°. It will beunderstood that any limitation on movement may be achieved bycontrolling the length of the slot. Additionally, limitation may beadjusted as desired to a precise degree by using stop members 251 whichmay comprise a screw or rivet or any other device mounted within theslot to limit travel of the post 248.

In the case of certain specific injuries or deformities, or in stillother instances, such as in the preparation and the manufacture ofprostheses, it is desirable to be able to provide a mechanical joint atthe knee position which can be molded into a plaster or fiberglass cast,or become an integral part of a prosthetic device. In light of the factthat the mechanical joints 32, 132 and 232 of the present inventionprovide an extremely close assimilation of the movement of a normalknee, the provision of joints which may become parts of other appliancesand/or a cast or casts or various orthotic devices is a furtherdesirable feature of the invention. This is accomplished as can be seenin FIGS. 13 through 15, by the provision of elongated parallel links 334and 335 to which a joint 332 may be riveted or otherwise attached as at337. The links 334 and 335 may be integrated into any prosthetic deviceor casts in order to provide the wearer with a natural knee jointmovement. While throughout this application the various aspects of theinvention have been illustrated and discussed with respect to anexemplary joint, it will be understood that joints are used in pairs onthe medial and lateral side of each knee joint.

Having now described a preferred embodiment of the invention, what isclaimed is:
 1. In an appliance for stabilizing a knee joint in sagittal,coronal and transverse planes, having leg grasping means for claspingthe appliance to the wearer's leg above and below the knee,meansdefining a mechanical joint at the medial and lateral sides of the knee,each comprising a pair of depending opposed femoral links, each saidlink terminating in an end portion, a pair of opposed upwardly extendingtibial links terminating in an end portion; said end portion of saidtibial links being disposed in overlapping relation to said end portionof said femoral links, cam means interconnecting each said end portionof said femoral links to a respective said end portion of said tibiallinks, said cam means being disposed at lateral and medial sides of theknee, each said cam means comprising a cam pin follower and a cammingslot means, each said cam pin follower means being fixedly positionedrelative to a link of one of said pairs of links and relativelydisplaceable relative to a link of the other of said pairs of linkswithin a respective camming slot means, said cam pin follower andcamming slot means forming a means for constraining the tibia to sliderearwardly relative to the femur for a predetermined distance during aninitial range of flexion of the knee from a straight leg position and,beyond said initial range of flexion to, thereafter, rotate relativethereto in a predetermined arcuate path, irrespective of the loadingapplied thereto by the leg of the wearer.
 2. An appliance according toclaim 1, wherein said initial range of flexion is about 25°.
 3. Anappliance according to claim 2, wherein said arcuate path is a circularsegment.
 4. An appliance according to claim 1, wherein said arcuate pathis a circular segment.
 5. An appliance according to claim 1, whereinsaid camming means comprises a pair of cam pin followers and a pair ofcamming slot means, said cam pin followers resting in a plane that istransverse to the longitudinal plane of the tibia of the wearer andpasses through a center point representing the center of the radius ofrotation of the femoral condyle of the wearer relative to the tibia, andsaid pair of camming slots comprising upper and lower camming slotswhich extend from said plane in directions above and below said plane,respectively.
 6. An appliance according to claim 5, wherein said initialrange of flexion is about 25°.
 7. An appliance according to claim 6,wherein said arcuate path is a circular segment.
 8. An applianceaccording to claim 5, wherein said arcuate path is a circular segment.9. An appliance according to claim 1, wherein said cam means isexclusively composed of components that are rigidly secured to at leastone or the other of said femoral and tibial links.
 10. In an appliancefor stabilizing a knee joint in sagittal, coronal and transverse planes,having leg grasping means for clasping the appliance to the wearer's legabove and below the knee,means defining a mechanical joint at the medialand lateral sides of the knee, each comprising a pair of dependingopposed femoral links, each said link terminating in an end portion, apair of opposed upwardly extending tibial links terminating in an endportion; and connecting means interconnecting each said end portion ofsaid femoral links to a respective said end portion of said tibiallinks, said connecting means being disposed at each of lateral andmedial sides of the knee and being comprised of elements which coact toform a movement control means for constraining the tibia to sliderearwardly relative to the femur for a predetermined distance throughoutan initial range of flexion of the knee from a straight leg positionand, beyond said initial range of flexion, to rotate relative theretoalong a predetermined arcuate path, irrespective of the loading appliedthereto by weighting of the leg of the wearer.
 11. An applianceaccording to claim 10, wherein said initial range of flexion is about25°.
 12. An appliance according to claim 11, wherein said arcuate pathis a circular segment.
 13. An appliance according to claim 10, whereinsaid arcuate path is a circular segment.